A chemical vapor deposition method (hereinafter, referred to as “CVD” method) is a film-formation process widely used in forming various metallic or metallic compound thin films. This is because a uniform thin film can be easily manufactured by the CVD method and the step coverage obtained by the CVD method is better than by a sputtering method. Particularly in recent years, a precious metal such as ruthenium or iridium has come to be used in manufacturing a thin film electrode material of a semiconductor device such as DRAM and FERAM. The CVD method is suitably used in a manufacturing process for such a precious metallic thin film.
In the CVD method, a raw-material chemical compound is gasified and transferred onto a substrate, and then decomposed and oxidized on the substrate, thereby precipitating or depositing a desired thin film constituting substance to obtain a thin film. Therefore, the raw material chemical compound for CVD preferably has a low melting point in order to vaporize easily, and causes a reaction rapidly on the substrate. As a compound having these characteristics, an organometallic compound is mentioned and generally used in a CVD method. The organometallic compound used herein is a complex compound having a target metal element for manufacturing a thin film used as the central metal, with which various substituents are coordinated.
As a raw material for forming a precious metallic thin film by CVD, various organic precious metallic compounds are known. Taking ruthenium as an example, a bis(ethylcyclopentadienyl)ruthenium represented by the following formula has been studied as an organic ruthenium compound to be put to practical use. This organic ruthenium compound is one of derivatives of ruthenocen(bis(cyclopentadienyl)ruthenium), which is a cyclopentadienyl complex having ruthenium as a central metal and two cyclopentadienyl groups coordinated therewith. 
The bis(ethylcyclopentadienyl)ruthenium has a low melting point and is liquid at room temperature, so that it is easy to handle. In addition, it has a high vapor pressure, so that the manufacturing efficiency of a thin film is high. Therefore, this is considered suitable for CVD raw material.
Furthermore, in view of reducing the manufacturing cost for a thin film and making effective use of resources, introduction of recycling technology for CVD raw material has been considered. To recycle the CVD raw material, it is necessary to separate and purify an unreacted compound efficiently from a used material. Since bis(ethylcyclopentadienyl)ruthenium has a high vapor pressure and a good thermal stability, an unreacted bis(ethylcyclopentadienyl)ruthenium is relatively easily separated and purified, and thus efficiently reutilized by using appropriate means such as distillation.
On the other hand, another organic ruthenium compound for CVD raw material, tris(β-diketonato)ruthenium represented by the following formula is also known. The organic ruthenium compound has ruthenium as a central metal and three β-diketones coordinated therewith. 
Tris(β-diketonato)ruthenium is characterized in that it can form a thin film having high adhesiveness to SiO2. It means that it can provide a thin film excellent in adhesiveness to a semiconductor substrate, which is often formed of SiO2 or a SiO2 film.